Thermoelectric devices

ABSTRACT

This disclosure relates to methods for manufacturing devices capable of functioning as thermoelectric generators and related objects by the process of additive manufacturing or by 3-D printing or by casting. This disclosure also particularly relates to the uses of the thermoelectric generators and related objects produced by these methods.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a continuation of U.S. patent applicationSer. No. 15/181,298, filed Jun. 13, 2016, which claims the benefit ofU.S. Provisional Patent Application Ser. No. 62/174,968, entitled“Thermoelectric Devices,” filed Jun. 12, 2015, which applications areincorporated in their entirety here by this reference.

BACKGROUND

Technical Field

This disclosure relates to the field of additive manufacturing. Thisdisclosure also relates to the field of 3-D printing. This disclosureparticularly relates to the fabrication of thermoelectric devices, suchas thermoelectric generators. This disclosure also relates to methodsfor employing additive-manufacturing systems and/or devices forproducing useful materials and/or objects, including thermoelectricdevices, such as thermoelectric generators.

Description of Related Art

There is currently considerable research and development effort beingdirected at the development of devices which are capable of generatingelectricity from low-level or waste energy sources. Among these devices,which are sometimes known as thermoelectric generators, are models inwhich a modest temperature difference can be used to generate anelectric current. Such devices rely on the incorporation of specialsubstances, called thermoelectric materials, which can generateelectricity from low-level temperature differences. These types ofdevices can be used to generate power in a wide variety of applications,and are expected to play a significant role in addressing the globalenergy crisis.

In addition to the challenge of developing efficient and cost-effectivethermoelectric materials, another impediment to the widespreadapplicability of thermoelectric generators is the cost and complexity ofassembling useful devices which incorporate them. Most such devices arecurrently assembled by hand using a variety of different materials,which not only makes them cost-prohibitive but also introducesunnecessary complication, lowers reliability and reproducibility, anddegrades their performance. Clearly, better fabrication methods areneeded to facilitate the widespread acceptance of thermoelectricgenerators.

Additive manufacturing refers to a family of technologies for buildingthree-dimensional (3-D) solid or partially-solid objects by sequentiallyor simultaneously depositing layers of materials according to a designproduced using a computer-aided design (CAD) software application. Thefamily of additive manufacturing (AM) techniques has proven useful forthe rapid production of complex prototypes as well as the manufacture ofcomplex and complicated objects, and is especially well-suited tofabricating complicated objects in a rapid and cost-effective manner.

Additive manufacturing can be used to create highly-customized complexparts and products that are difficult or impossible to manufacture usingtraditional technologies. This technology can also be used to rapidlycreate prototype objects which could take much longer to produce byother means. This technology can also be used to create objects at alower cost than they could be produced using other means.

One especially useful form of additive manufacturing is known as 3-Dprinting. In 3-D printing, multiple layers of material (referred togenerally as the ‘build material’) are laid down successively to producea three-dimensional object.

There are several major 3-D printing technologies differing mainly inthe way successive layers are built to create the final 3-D object. Somemethods use melting or softening and deposition of the build material toproduce the layers of the growing object. For example, fused-depositionmodeling (FDM) works by extruding melted plastic or metal, oftensupplied in the form of filaments or wires, through an extrusion nozzleto form the successive layers. On the other hand, selective lasersintering (SLS) works by laying down a thin layer of powdered metal,plastic, ceramic, or glass and then sintering the intendedcross-sectional area of each layer to produce the desired object. Powderprinting works similarly, except that the layers of powdered materialswhich are laid down are then printed over using a technology such as anink-jet printer to create the cross-sectional image of the desiredobject. Stereolithography (or stereolithographic assembly, SLA) is basedon photocuring (polymerizing) liquid materials such as polymer resins byapplying external energy sources such as ultraviolet (UV) or visiblelight or electron-beam irradiation to produce each successive layer of asolid object. Each of these additive manufacturing techniques hasimportant applications in the fields of prototyping and manufacturing.

Two relevant publications which detail current research efforts onthermoelectric materials and thermoelectric generators include G. J.Snyder and E. Toberer, Nature Materials 7, 105 (2008) and P. Sheng, Y.Sun, F. Jiao, C. Di, W. Xu, and D. Zhu, Synthetic Metals 193, 1-7(2014). The entire content of these publications is incorporated hereinby reference.

The illustration in FIG. 1 is taken from FIG. B1 in G. J. Snyder and E.Toberer, Nature Materials 7, 105 (2008), and shows a schematicrepresentation of a thermoelectric generator. The outer,non-electrically conducting substrates 10 a, 10 b are shown in gray,these are typically made from materials such as poly(dimethylsiloxane)(PDMS) or a poly(imide) such as Kapton®, which are familiar commercialmaterials to those skilled in the art. A series of thermoelectricelements 12 a, 12 b, or legs, is represented as vertical members withsquare cross sections. A series of metal interconnects 14 a providesthermal connections between pairs of legs at the top of the generator,while another set of metal interconnects 14 b provides electricalconnections between pairs of legs at the bottom of the generator. Theseconnections alternate, so that the thermal connections occur betweendifferent legs than do the electrical connections. The flow ofelectrical current is thus up through an n-type leg, across the thermalconnector, down through an p-type leg, across the electrical connector,and then up again through the next n-type leg, and so on until itreaches the distal terminal and exits the thermoelectric generator.

Although additive manufacturing would appear to provide an excellentprocess for both prototyping and manufacturing thermoelectricgenerators, three major impediments have thus far hindered thisapproach. First, thermoelectric generators are generally constructedfrom a heterogeneous set of materials, including polymers, carbon forms,metals, plastics, and other materials, which generally cannot be 3-Dprinted using any one 3-D printer. Thus, the assembly of thermoelectricgenerators has been restricted to manual methods. The other impedimenthas been that it has not been possible to 3-D print the types ofthermally- and electrically-conducting materials which are required forthe construction of efficient thermoelectric generators. Such materialshave demanding properties which require very specific operationalparameters, and have thus far proven impossible to 3-D print. The thirdimpediment is specific to stereolithographic assembly (SLA), a preferredmethod of 3-D printing due to its many advantageous features. A drawbackof SLA, however, is that it is generally restricted to a singlematerial. That is, only one type of material can be 3-D printed at atime. Overcoming these three impediments would be expected to lead tothe capability to mass-produce thermoelectric generators for a widevariety of applications. This capability, in turn, would enable a widearray or new and novel products with potential applications in homeheating, automotive power, industrial generation, aerospace operations,marine environments, and widely-distributed power generation, among manyother applications. The electricity generated by these devices could beused to power electronic devices such as energy-storage devices,communications devices, medical devices, ballistic monitors, aircraftand aerospace vehicles, as well as numerous other items.

Thus, the ability to combine efficient thermoelectric materials with amore-efficient and manufacturable design, reduced numbers of materials,and a practical electrically-conducting 3-D printing process wouldenable a large family of new and novel thermoelectric generators withapplicability to a wide variety of fields and industries.

SUMMARY

This disclosure relates to the field of electrical power generation.This disclosure also relates to the field of additive manufacturing or3-D printing. This disclosure also relates to the field ofthermoelectric generators.

Surprisingly, the foregoing challenges can be solved by re-designing thethermoelectric generator and/or increasing its symmetry to permit thefabrication of fewer distinct parts, as well as eliminating some of thematerials of construction and developing novel methods for the 3-Dprinting and assembly of the electrically- and thermally-conductivecomponents of the devices. Together, these improvements make possiblethe rapid, facile, and inexpensive fabrication of thermoelectricgenerators and related devices.

In the present invention, the thermoelectric generator is redesigned sothat all of the p-type legs and all of the n-type legs are each 3-Dprinted as a separate, single, and nearly-identical component.

In the present invention, the metal interconnect pieces are replaced bythe same 3-D printable material used to print the legs. Thus, the n-typeleg structure has n-type interconnect pieces, and the p-type legstructure hasp-type interconnects.

In the present invention, the metal interconnect pieces can also bereplaced by an undoped electrically-conducting material which is neithern-type nor p-type but which can nonetheless conduct electricity betweenthe n-type and p-type legs.

The n-type and p-type dopants may be selected from a wide variety ofmaterials well-known to those skilled in the art.

Although the n-type and p-type materials sometimes show reducedelectrical conductivity as compared to undoped materials, theirconductivity must necessarily be sufficient for the operation of thethermoelectric generator because the power which is generated by thedevice already flows through each of the p-type and n-type legs.

In addition to reducing the materials requirements and simplifying the3-D printing process, fabricating the interconnect pieces from the samematerial as is used to fabricate the n-type and p-type legs provides theadditional advantage of eliminating any contact resistance which may beobserved between the dissimilar materials of the legs and theinterconnect pieces. This results in improved electrical conductivitythroughout the device and acts to attenuate any conductivity lossesresulting from the reduced conductivity of the non-metallicinterconnects.

The 3-D printing process can be carried out onto any of a number ofsubstrates, illustrated in FIG. 1 in gray, which can therefore be chosenfor their particular mechanical, thermal, or electrical properties.

The orientation of the 3-D printing process can be adjusted to optimizethe properties of the final 3-D printed components. As one example, 3-Dprinting the individual n-type and p-type components at an angle whichis 90° to the plane of the substrate will orient the individual 3-Dprinted layers (laminae) along the long axis of the legs, facilitatingelectrical flow through them and further reducing contact resistancewith the interconnects.

In addition to 3-D SLA printing, this disclosure anticipates that thepresent components and devices can also be fabricated using any otheradditive manufacturing method, including but not limited to powderprinting, FDM, SLS, inkjet or multijet techniques, or any other suchadditive manufacturing technique which is known to those skilled in theart.

The simplicity of the n-type and p-type components in the presentdisclosure further means that in addition to being fabricated byadditive manufacturing methods, they can also simply be cast as singleobjects. For example, the n-type and p-type materials can each beseparately placed into a mold or similar form and irradiated to producethe respective n-type and p-type components. This method of fabricationcan lead to even greater manufacturing speeds and lowered manufacturingcosts.

These, as well as other components, steps, features, objects, benefits,and advantages, will now become clear from a review of the followingdetailed description of illustrative embodiments, the accompanyingdrawings, and the exemplary features.

BRIEF DESCRIPTION OF DRAWINGS

The drawings are of illustrative embodiments. They do not illustrate allembodiments. Other embodiments may be used in addition or instead.Details that may be apparent or unnecessary may be omitted to save spaceor for more effective illustration. Some embodiments may be practicedwith additional components or steps and/or without all of the componentsor steps that are illustrated. When the same numeral appears indifferent drawings, it refers to the same or like components or steps.

FIG. 1 is a schematic illustration of a thermoelectric generator takenfrom FIG. B1 in G. J. Snyder and E. Toberer, Nature Materials 7, 105(2008). This generator contains a 9×6 matrix of square cross-sectionalthermoelectric elements, or legs, for a total of 54 legs.

FIG. 2 is an embodiment of a single n-type leg structure. This figureshows the array of n-type legs which is 3-D printed onto a substrateusing the n-type doped material. In this example, the bottom rectangularboxes (the interconnects) are 2×2×1 mm and the vertical blocks which areattached to them (the thermoelectric elements or legs) are 2×2×5 mm.

FIG. 3 is an embodiment of a single p-type leg structure. This figureshows the array of p-type legs which is 3-D printed onto a substrateusing the p-type doped material. In this example, the bottom rectangularboxes (the interconnects) are 2×2×1 mm and the vertical blocks which areattached to them (the thermoelectric elements or legs) are 2×2×5 mm.

FIG. 4 is a drawing of an embodiment of an assembled 3-D printablethermoelectric generator. This figure shows how the components in FIGS.2 and 3 are assembled to obtain an intact device in which the currentflows in series row by row. The current flows by going down one row tothe end, after which it moves to the next row by a connector and thenflows down the next row in the opposite direction. The electricalcurrent then continues flowing in this pattern until it reaches theterminal contact at the other end.

FIG. 5 is a Photograph of 3-D printed mock-ups of the separate n-typeand p-type components, showing the regular arrays of 2×2 mm legs printedonto a mock-up of the substrate to form single n-type or p-typecomponents.

FIG. 6 is an elevation view of the assembled 3-D printed thermoelectricgenerator, comprising mock-ups of the n-type and p-type componentstogether with simulated substrate layers on the outer edges.

FIG. 7 is a perspective view of the assembled 3-D printed thermoelectricgenerator mock-up showing the full array of 9×6 legs sandwiched betweenthe outer substrate layers and linked together by the top (thermal) andbottom (electrical) interconnects. The external electrical contacts areshown in the foreground at the bottom of the thermoelectric generator.

FIG. 8 is a perspective view of the assembled 3-D printed thermoelectricgenerator mock-up showing the full array of 9×6 legs sandwiched betweenthe outer substrate layers and linked together by the top (thermal) andbottom (electrical) interconnects. The external electrical contacts areshown at bottom right on the thermoelectric generator.

FIG. 9 is a Photograph of electrically-conducting prototypes of then-type and p-type components of a 6×6 leg thermoelectric generator 3-Dprinted onto a flexible PDMS substrate.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Illustrative embodiments are now described. Other embodiments may beused in addition or instead. Details that may be apparent or unnecessarymay be omitted to save space or to achieve a more effectivepresentation. Some embodiments may be practiced with additionalcomponents or steps and/or without all of the components or steps thatare described.

This disclosure is illustrated by the following examples that are not tobe construed as limiting the disclosure in scope to the specificprocedures or products described in them.

This disclosure relates to the fabrication of devices useful for thegeneration of electrical power from waste heat or modest differences intemperature. This disclosure also relates to the additive manufacture ofdevices useful for generating electrical power. This disclosure alsorelates to the 3-D printing of devices useful for generating electricalpower.

EXAMPLE 1

In one embodiment, a sheet of the non-conducting polyimide Kapton®substrate 100 of the appropriate thickness was affixed to the buildplate of a commercial stereolithographic printer (Ember from Autodesk,San Francisco, Calif.). An electrically-conducting photopolymer resinwas prepared by mixing together about 65% to about 75% of Photomer 4050(PEG 200 diacrylate, IGM Resins, St. Charles, Ill.), about 15% to about25% of SR494 from Sartomer Americas (ethoxylated pentaerythritoltetraacrylate, Exton, Pa.), about 2.0 weight % of BAPO(phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide), IGM Resins,Charlotte, N.C.), and about 40 mg of single-walled carbon nanotubes(SWCNT) obtained from OCSiAl (Palo Alto, Calif.), and doped with p-typematerial to obtain about 50 mL of an electrically-conducting p-typephotocurable resin. Preferably, Photomer 4050 is about 73% of the totalresin. The resin was dispersed by power sonication with a Branson(Danbury, Conn.) Digital Sonifier model 250 fitted with a model 102Cprobe followed by agitation using a magnetic stirrer. Theelectrically-conducting p-type photocurable resin was placed in thebuild vat of the Ember printer and a 6×6 array 102 of 2 mm×2 mm legs 110with 0.5 mm heights on 2 mm×5 mm interconnects 104 was printed onto thenon-conducting Kapton substrate 100 to produce the p-type component. Thearray 102 comprises a series of interconnects 104 spaced apart from eachother. Each interconnect has a first end 106 and a second end 108opposite the first end 106. Stemming away from the first end 106 is theleg 110. The leg 110 comprises a proximal end 112 and a distal end 114.The proximal end 112 is operatively connected to the first end 106 ofthe interconnect 104.

Separately, a similar electrically-conducting resin was prepared asdescribed above and doped with n-type material to obtain about 50 mL ofa separate electrically-conducting n-type photocurable resin, which wassimilarly dispersed by power sonication with a Branson (Danbury, Conn.)Digital Sonifier model 250 fitted with a model 102C probe followed byagitation using a magnetic stirrer. The p-type photocurable resin wasremoved from the Ember printer and the electrically-conducting n-typephotocurable resin was placed in the build vat of the Ember printer.Another sheet of the non-conducting Kapton® substrate 200 of theappropriate thickness was affixed to the build plate of the Emberprinter, and a 6×6 array 202 of 2 mm×2 mm legs 210 with 0.5 mm heightson 2 mm×5 mm interconnects 204 was printed onto the non-conductingKapton® substrate 200 to produce the n-type component. The array 202comprises a series of interconnects 204 spaced apart from each other.Each interconnect has a first end 206 and a second end 208 opposite thefirst end 206. Stemming away from the first end 206 is the leg 210. Theleg comprises a proximal end 212 and a distal end 214. The proximal end212 is operatively connected to the first end 206 of the interconnect204.

The p-type and n-type components were then removed from their respectivebuild plates, washed with isopropanol and water to remove unreactedresin components, and then exposed to additional irradiation by lightwith a significant 405 nm component to complete the polymerizationprocess, in a manner which is well-known to one skilled in the art. Bothpieces were then treated with (e.g. coated with, dipped into, or paintedwith) electrically-conducting liquid or paste known in the trade aspotting paste, which is available at sources familiar to those skilledin the art, in order to form good electrical contact between thecomponents. The coating or dipping process is accomplished in such a waythat just the free distal ends 114, 214 of the thermoelectric legs 110,210 were wetted, after which the un-type and p-type components werefitted together to form the completed thermoelectric device supported ona flexible Kapton® substrate. Preferably, the array of p-type components102 is assembled with the array of n-type components 202 such that thedistal ends 114 of the p-type legs 110 are operatively connected to arespective second end 208 of the second set of n-type interconnects 204,and the distal ends 214 of the n-type legs 210 are operatively connectedto a respective second end 108 of the first set of p-type interconnects104 to form a thermoelectric generator. The device can optionally befitted into a larger enclosure or left as is, with the Kapton® piecesoptionally trimmed to fit the intended space. The device can then befilled with a suitable non-conducting substance, or left filled withair, or a vacuum can be pulled on the device in order to electricallyinsulate it. The resulting thermoelectric generator can then be used ina wide variety of applications.

EXAMPLE 2

In another embodiment, a prototype thermoelectric generator wasfabricated by first preparing an electrically non-conducting acrylateresin by mixing together about 65% to about 75% of Photomer 4050 (PEG200 diacrylate, IGM Resins, St. Charles, Ill.), about 15% to about 25%of SR494 from Sartomer Americas (ethoxylated pentaerythritoltetraacrylate, Exton, Pa.), about 2.0 weight % of BAPO(phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide), IGM Resins,Charlotte, N.C.), and agitated for 24 hours using a magnetic stirrer toobtain about 50 mL of resin. Preferably, the Photomer is about 73% ofthe total resin. The non-conducting substrate layer 100 of an arbitrarysize was printed onto the build plate of a commercial stereolithographicprinter (Ember from Autodesk, San Francisco, Calif.). Anelectrically-conducting photopolymer resin was prepared by mixingtogether about 65% to about 750% of Photomer 4050 (PEG 200 diacrylate,IGM Resins, St. Charles, Ill.), about 15% to about 25% of SR494 fromSartomer Americas (ethoxylated pentaerythritol tetraacrylate, Exton,Pa.), about 2.0 weight % of BAPO(phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide), IGM Resins,Charlotte, N.C.), and about 40 mg of single-walled carbon nanotubes(SWCNT) obtained from OCSiAl (Palo Alto, Calif.), and doped with p-typematerial to obtain about 50 mL of a separate electrically-conductingp-type photocurable resin. Preferably, the Photomer is about 73% of thetotal resin. The resin was dispersed by power sonication with a Branson(Danbury, Conn.) Digital Sonifier model 250 fitted with a model 102Cprobe followed by agitation using a magnetic stirrer. Theelectrically-conducting p-type photocurable resin was placed in thebuild vat of a commercial stereolithographic printer (Ember fromAutodesk, San Francisco, Calif.) and printed onto the non-conductingacrylate substrate 100 to produce a p-type component comprising 6×6arrays 102 of 2 mm×2 mm legs 110 with 0.5 mm heights on 2 mm×5 mminterconnects 104 printed onto the non-conducting acrylate substrate 100as in Example 1.

Separately, a similar electrically-conducting resin was prepared anddoped with n-type material to obtain about 50 mL of a separateelectrically-conducting n-type photocurable resin, which was similarlydispersed by power sonication with a Branson (Danbury, Conn.) DigitalSonifier model 250 fitted with a model 102C probe followed by agitationusing a magnetic stirrer. The electrically-conducting n-typephotocurable resin was placed in the build vat of a commercialstereolithographic printer (Ember from Autodesk, San Francisco, Calif.)and printed onto the non-conducting acrylate substrate 200 to produce ann-type component comprising 6×6 arrays 202 of 2 mm×2 mm legs 210 with0.5 mm heights on 2 mm×5 mm interconnects 204 printed onto thenon-conducting acrylate substrate 200 as in Example 1. The p-type andn-type components were then removed from their respective build plates,post-processed, and assembled as described in Example 1 to obtain thethermoelectric device supported on a flexible acrylate substrate 100,200.

EXAMPLE 3

In another embodiment, a prototype thermoelectric generator wasfabricated by first preparing an electrically non-conductingphotopolymer resin by mixing together about 65% to about 75% of Photomer4050 (PEG 200 diacrylate, IGM Resins, St. Charles, Ill.), about 15% toabout 25% of SR494 from Sartomer Americas (ethoxylated pentaerythritoltetraacrylate, Exton, Pa.), about 2.0 weight % of BAPO(phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide), IGM Resins,Charlotte, N.C.), and agitated for 24 hours using a magnetic stirrer toobtain about 50 mL of resin. Preferably, the Photomer was about 73% ofthe total resin. The non-conducting substrate layer 100 of an arbitrarysize was printed onto the build plate of a commercial stereolithographicprinter (Ember from Autodesk, San Francisco, Calif.). Anelectrically-conducting photopolymer resin was prepared by mixingtogether about 65% to about 75% of Photomer 4050 (PEG 200 diacrylate,IGM Resins, St. Charles, Ill.), about 15% to about 25% of SR494 fromSartomer Americas (ethoxylated pentaerythritol tetraacrylate, Exton,Pa.), about 2.0 weight % of BAPO(phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide), IGM Resins,Charlotte, N.C.), and about 40 mg of single-walled carbon nanotubes(SWCNT) obtained from OCSiAl (Palo Alto, Calif.), to obtain about 50 mLof resin. Preferably, the Photomer was about 73% of the total resin. Theresin was dispersed by power sonication with a Branson (Danbury, Conn.)Digital Sonifier model 250 fitted with a model 102C probe followed byagitation using a magnetic stirrer. The combined mixture was placed inthe build vat of a commercial stereolithographic printer (Ember fromAutodesk, San Francisco, Calif.) and a 6×6 pattern of 2 mm×5 mminterconnects 104 was printed onto the non-conducting acrylate substrate100 to produce a non-doped, electrically-conducting interconnect layerfor the p-type component. A second electrically-conducting resin wasprepared as described above and doped with p-type material to obtain aseparate electrically-conducting p-type photocurable resin. Theoriginal, non-doped photocurable resin was removed from the Emberprinter and the p-type photocurable resin was placed in a vat on theEmber printer. A 6×6 array of 2 mm×2 mm p-type legs 110 with a height of0.5 mm was then printed onto the non-doped 2 mm×5 mm interconnects 104to complete the p-type array 102, which was then removed from the Emberprinter and washed and post-processed as described in Example 1. A freshlayer of the original non-conducting acrylate resin was then printedonto a fresh build plate of the Ember printer to provide a newnon-conducting substrate 200. The non-conducting acrylate resin wasremoved from the Ember vat, and the original non-dopedelectrically-conducting resin was placed in a vat on the Ember and usedto print a 6×6 pattern of 2 mm×5 mm interconnects 204 onto the freshnon-conducting acrylate substrate 200 to produce a non-doped,electrically-conducting interconnect layer for the n-type component. Athird electrically-conducting photocurable resin was prepared asdescribed above and doped with n-type material to obtain a separateelectrically-conducting n-type photocurable resin. The original,non-doped electrically-conducting photocurable resin was removed fromthe Ember printer and the n-type photocurable resin was placed in a vaton the Ember printer. A 6×6 array of 2 mm×2 mm n-type legs 210 with aheight of 0.5 mm was then printed onto the non-doped 2 mm×5 mminterconnects 204 to complete the n-type array 202, which was thenremoved from the Ember printer and washed and post-processed asdescribed in Example 1. The p-type and n-type components were thenassembled as described in Example 1 to obtain the thermoelectric devicewithout doped interconnects and supported on a flexible acrylatesubstrate.

EXAMPLE 4

In another embodiment, a prototype thermoelectric generator wasfabricated by first preparing an electrically non-conductingpolydimethylsilane substrate by mixing Sylgard 184 Silicone ElastomerKit Base and Curing Agent (Dow Corning, Midland, Mich.) in a 10:1 (w/w)ratio, respectively, casting the mixture into a 2.4 cm×4.0 cm mold, andthen curing the mixture by heating it at 75° for 120 minutes to obtain asolid non-conducting PDSM substrate 100. An electrically-conductingphotopolymer resin was then prepared by mixing together about 65% toabout 75% of Photomer 4050 (PEG 200 diacrylate, IGM Resins, St. Charles,Ill.), about 15% to about 25% of SR494 from Sartomer Americas(ethoxylated pentaerythritol tetraacrylate, Exton, Pa.), about 2.0weight % of BAPO (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide), IGMResins, Charlotte, N.C.), and about 40 mg of single-walled carbonnanotubes (SWCNT) obtained from OCSiAl (Palo Alto, Calif.), to obtainabout 50 mL of resin. Preferably, the Photomer was about 73% of thetotal resin. The resin was dispersed by power sonication with a Branson(Danbury, Conn.) Digital Sonifier model 250 fitted with a model 102Cprobe followed by agitation using a magnetic stirrer. A second mold witha height of 0.5 mm was placed over the top of the base mold and theundoped, electrically-conducting resin was spread into the cavities ofthe second mold to form a 6×6 pattern of 2 mm×5 mm interconnects 104 onthe non-conducting PDMS substrate 100. The mold assembly was exposed tosunlight for 3 minutes to further cure the resin and then a third moldwith a height of 0.5 mm was placed on top of the two previous molds. Asecond electrically-conducting resin was prepared and doped with p-typematerial as described in Example 3 to obtain an electrically-conductingp-type photocurable resin. The p-type photocurable resin was spread intothe cavities of the third mold to form a 6×6 pattern of p-type legs 110on top of the non-doped, electrically-conducting second (interconnect)layer 104 to form a p-type array 102 as in Example 1. Separately,another 2.4 cm×4.0 cm electrically non-conducting polydimethylsilanesubstrate was formed inside a base mold and cured by heating thesilicone mixture at 750 for 120 minutes to obtain a non-conductingsubstrate 200. A second n-type mold was placed over the base mold andthe undoped electrically-conducting resin was applied to the mold tocreate the 6×6 pattern of 2 mm×5 mm interconnects 204 on thenon-conducting PDMS layer. A third electrically-conducting resin wasprepared and doped with n-type material as described in Example 3 toobtain an electrically-conducting n-type photocurable resin. A thirdn-type mold was placed over the second mold and the n-type photocurableresin was spread into the cavities of the third mold to form a 6×6pattern of n-type legs 210 on top of the non-doped,electrically-conducting second (interconnect) layer 204 to form ann-type array as in Example 1. After washing and post-curing, both thep-type and n-type components were removed from their respective moldsand washed and post-processed as described in Example 1. The p-type andn-type components were then assembled as described in Example 1 toobtain the molded thermoelectric device supported on a flexible acrylatesubstrate.

All articles, patents, patent applications, and other publications thathave been cited in this disclosure are incorporated herein by reference.

The phrase “means for” when used in a feature is intended to and shouldbe interpreted to embrace the corresponding structures and materialsthat have been described and their equivalents. Similarly, the phrase“step for” when used in a feature is intended to and should beinterpreted to embrace the corresponding acts that have been describedand their equivalents. The absence of these phrases from a feature meansthat the feature is not intended to and should not be interpreted to belimited to these corresponding structures, materials, or acts, or totheir equivalents.

Relational terms such as “first” and “second” and the like may be usedsolely to distinguish one entity or action from another, withoutnecessarily requiring or implying any actual relationship or orderbetween them. The terms “comprises,” “comprising,” and any othervariation thereof when used in connection with a list of elements in thespecification or features are intended to indicate that the list is notexclusive and that other elements may be included. Similarly, an elementpreceded by an “a” or an “an” does not, without further constraints,preclude the existence of additional elements of the identical type.

The abstract is provided to help the reader quickly ascertain the natureof the technical disclosure. It is submitted with the understanding thatit will not be used to interpret or limit the scope. In addition,various features in the foregoing detailed description are groupedtogether in various embodiments to streamline the disclosure.

What is claimed is:
 1. A method of fabricating a thermoelectric device,comprising: a. operatively connecting a first set of interconnects withrespective p-type legs to form an array of p-type components, the firstset of interconnects comprising a plurality of interconnects, eachinterconnect comprising a first end and a second end opposite the firstend, each p-type leg comprising a proximal end and a distal end, whereinthe proximal end of each p-type leg is operatively connected to thefirst end of the respective interconnect of the first set ofinterconnects; b. operatively connecting a second set of interconnectswith respective n-type legs to form an array of n-type components, thesecond set of interconnects comprising a plurality of interconnects,each interconnect comprising a first end and a second end opposite thefirst end, each n-type leg comprising a proximal end and a distal end,wherein the proximal end of each n-type leg is operatively connected tothe first end of the respective interconnect of the second set ofinterconnects; c. operatively connecting the array of p-type componentsto a first non-conducting substrate; d. operatively connecting the arrayof n-type components to a second non-conducting substrate; and e.assembling the array of p-type components with the array of n-typecomponents to form a thermoelectric generator wherein the distal ends ofthe p-type legs are directly connected to a respective second end of thesecond set of interconnects, and the distal ends of the n-type legs aredirectly connected to a respective second end of the first set ofinterconnects to form a thermoelectric generator.
 2. The method of claim1, further comprising enclosing the thermoelectric generator in acontainer.
 3. The method of claim 1, wherein the first and second setsof interconnects and the p-type and n-type legs are produced by additivemanufacturing.
 4. The method of claim 3, wherein the additivemanufacturing is selected from the group consisting of 3-D printing,stereolithography, fused-deposition modeling, and inkjet printing. 5.The method of claim 1, wherein the first and second sets ofinterconnects and the p-type and n-type legs are produced by casting. 6.The method of claim 1, wherein an orientation of printing direction ismodified in order to optimize specific properties of the thermoelectricgenerator.
 7. The method of claim 1, wherein the distal ends of thep-type legs and the n-type legs are treated with electrically-conductingliquid.
 8. The method of claim 1, wherein the first and secondnon-conducting substrates each comprises PEG 200 diacrylate; ethoxylatedpentaerythritol tetraacrylate,phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.
 9. A method offabricating a thermoelectric device, comprising: a. operativelyconnecting an array of p-type components to a first non-conductingsubstrate; b. operatively connecting an array of n-type components to asecond non-conducting substrate; and c. stacking the array of p-typecomponents with the array of n-type components to form a thermoelectricgenerator, wherein the array of p-type components comprises a first setof interconnects operatively connected to respective p-type legs to formthe array of p-type components, the first set of interconnectscomprising a plurality of interconnects, each interconnect comprising afirst end and a second end opposite the first end, each p-type legcomprising a proximal end and a distal end, wherein the proximal end ofeach p-type leg is operatively connected to the first end of therespective interconnect of the first set of interconnects; and whereinthe array of n-type components comprises a second set of interconnectsoperatively connected to respective n-type legs to form the array ofn-type components, the second set of interconnects comprising aplurality of interconnects, each interconnect comprising a first end anda second end opposite the first end, each n-type leg comprising aproximal end and a distal end, wherein the proximal end of each n-typeleg is operatively connected to the first end of the respectiveinterconnect of the second set of interconnects.
 10. The method of claim9, wherein the distal ends of the p-type legs are operatively connectedto a respective second end of the second set of interconnects, and thedistal ends of the n-type legs are operatively connected to a respectivesecond end of the first set of interconnects to form a thermoelectricgenerator.
 11. The method of claim 9, wherein the first and second setsof interconnects and the p-type and n-type legs are produced by additivemanufacturing.
 12. The method of claim 11, wherein the additivemanufacturing is selected from the group consisting of 3-D printing,stereolithography, fused-deposition modeling, and inkjet printing. 13.The method of claim 9, wherein the first and second sets ofinterconnects and the p-type and n-type legs are produced by casting.14. The method of claim 9, wherein an orientation of printing directionis modified in order to optimize specific properties of thethermoelectric generator.
 15. The method of claim 9, wherein the distalends of the p-type legs and the n-type legs are treated withelectrically-conducting liquid.
 16. The method of claim 9, wherein thefirst and second non-conducting substrates each comprises PEG 200diacrylate.
 17. The method of claim 9, wherein the first and secondnon-conducting substrates each comprises ethoxylated pentaerythritoltetraacrylate.
 18. The method of claim 9, wherein the first and secondnon-conducting substrates each comprisesphenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.